Antioxidant or age-resister



10 rubber with minimum UNITED ;r-eT NTjgorrl i- ALBERT M. cLIrronn; corfnxnoivi, olrro nssrenon'ro rnneoom'rmn TIRE & RUB- BER COMPANY, orAKRON, 01:10, A 'fcdnrom'rxolv or 0310 1% Drawing. Original alication'fiieain rnr, 192s} fsiiiiib; 26838 i'pieaea ana 'thi pplicationfiled March 8, 1929.

This inventionrelates to the t eatment or rubber and ithasi'particularrelationto a method of treatment whereby the durabilityof rubber'compoundsis materially enhanced. This applicationds adivisionof application Serial No. 268,387, filed April 7,1928,

, 'One object of thelinvention isto provide an antioxidant orage-retarder for lubb61 COII1- pounds that may be incorporated into theexpenditure of time and effort. 1

Another object of the invention is to provide a material of the abovedesignated-charr acter, which is substantially nOn QdOrQusand-Structural di -Y non-toxic.

Heretofore, it has'been observed that certain compounds, whenincorporated into rubber, materially reduce the frate of fdeteriora tioncaused bythe actionyofflightand air upon the rubber?Theseicompoundsftherefore, act as preservatives,greatly'increasing thelife of the rubbercinto which they are incorporated. iThegco'mpopnds,although they act as preservatives, have littleorc no effect as 5accelerators ofvulcanization. They may-be:

i p t dinto most s an a d bb 66 1. pounds prior to vulcanization?without appreciably disturbing; the so-called balance of the formula.Although many substances have been proposed for this purpose (forexeample, hydroquinone, para nitroso amino ph o v e o c r ea); most p themate; rials thus far tested have not proved to b e satisfactory in allrespects. Somesubstances,

c while fairly eificient as antioxidants, are high ly toxic, andgtheirutilization irreq e uy'rs sults in poisoning of the'workmen employed inhandling the rubber. Other materials are difficult to distributeuniformly through the 40' rubber. Still other materials of this class,While they may bereason'ably satisfactory-in other respects, are undulyexpensive tomanu= facture, and.their general juse isiconseguentlyimpractical. r

This invention 'consistsin 'the discovery ;seamgangster;

aminesofthe-type:

in which and TRLrepresent hydrocarbon rad1cals, part1 cularly aryl,radicals, are excelthat 'the 'sulfur remiss products of certain lentantioxidants, substantially free frommost of the obj ectionable featuresheretofore I encountered with regard to most of the antioxidantsheretofore employed. One specific example of a compound of this "classis thio diphenylamine, which has the following material may be preparedby heating sulfur and diphenylamine together in an autoclave at arelatively high temperature and pressure. v However, a betterinethodlfor thexpreparation of: the P compound consists inheatingcafmixture of diphenylamine and sulfurjtogetherin the-presence ofa trace of iodine, Preferably, the iodine should equal aPPT Xi 1Y; /2percen y; w g t f amine employed; The reaction temperature may varysomewhat, but for best results should range from'180' to C. In anyevent, the mixture should be heated'untilone 'molofhydro'gensulphide isevolvedflt c v g Thefevolution' of a mol ofhydrogedsul phfide usuallyrequires tento fifteen minutes. At the endofthat time, thereactionproduct may bepermitted to cool. The cooled product sets into-a-hard mass or cake, which may be pulverized and employed as anantioxidant without v further purification, although for beeresue it ispre ra fio p ri y h me s a convenient solvent for example; alcohol, 'andthen pouring the solution'into wate'r. The reaction product of thesulfur and the amine, being insoluble in and ether. The reaction takingplace during the course of preparation of the material may berepresented as follows:

The method outlined for v the preparation of thio diphenylamine isequallyapplicab'le he pr pa ti pf.ar l arge .number of compounds of thisclass. f1 or example, it may be employed in the preparation ofsuchducted upon the unaged samples. The results of these tests are indicatedin the following tables.

Thiio dllihenylamine before aging m r a hio.p ny maph hylam- 1 i inemelting point 178 C. thio-beta-di- I 5m 1 3 Percent Timeol pres- Percentnaphthylam1ne,me1ting point about 280 0., euro in i I I fife- Weight andthio phenyl-alcpha-napthylamine, melt- 3;: 53, 47; Br re increase ingpoint J The .reactions taking place in the preparation'of thelattersubi0 12 :35 stancesiiiay, respect vely, be representedby g, f; $32 thefollowing structural formulae:

. 1'1 I 11'! v j r I N sH ,BH 7 V s (Phenyl-beta-naphthylamine) (Thloplienyhbeta-n'aphth'ylamlne) a N N H sHSH j H s v(Beta-beta-dinaphthylamine) "rhio-be'm-bm-dinapmh iamine All "of, thesesubstancesmay be employed in .4 'f 9m most of. the standard rubbercompounds with 40 15 52 I 22 g .19 40 25 .91 1 70 .15 very satisfactoryresults The following is 40 36 m m 53 a specific example of a compoundthat yields an excellent product'when any Of the mate- Thtophenyl-beta-n'aphthglamine before aging rials justdiscussed are employedas antioxid t T i. 40 .13 39 105 880 5- so 40 2a .83, 810 70 40 30 122 i180 "795 I I Flirts After aging Extracted rubber '100 1 j y I 4o 17 59125 830 .09 Zmc oxlde I 5 .40 Y 28 108' ,775 .07 Sulfur... i 4. 4o 40156 110 710 .28 Stearic acid :1.5 i "j e a' n y tietramine ug uThw-beta-beta-dmaphthglamme before aging Antioxidant 1 40 17 54 I no 855I 40 23 as 820 p 0 v 34 135 760 Samples of 'materialprepared in accord-After (win ance with'the preceding formula Were-vulg ca ne nd, 9 5 e Ofsampleawes th 30 raw 1 w m w 4 ie d p y walteststqa m h l y 98:33:: t 33it? 122 it; 13% sile strength and elast city before aging.

From the tables it will be apparent that the thio amines discussed arehighly eflioient antioxidants, and that the compounds into which theywere incorporated resisted the action of. oxygen in a highlysatisfactory manner even under the relatively severe conditions to whichthey were subjected during the test. Under similar conditions, samplescontaining no antioxidant are reduced to resinous masses practicallydevoid of tensile strength and elasticity.

7 These materlals are substantially nonodorous, non-toxic, and mayreadily-be re- 7 duced to impalpable powders that, may be in termixedwith the rubber with greatest ease. The compounds may also be easilyprepared from relatively inexpensive materials. It is March, 1929;

evident, therefore, that they are in all respects highly satisfactory asantioxidants.

' Although I have described in detail only the preferred embodiments ofthe invention, it will be apparent to those skilled in the art that theinvention is not so limited, but that various minor modifications may bemade therein without departing from the spirit of the invention or fromthe scope of the appended claims.

What I claim is: p 1. A method of preserving rubber which comprisesincorporating therein the reaction product of beta-beta-dinaphthylamineand sulphur, said product having been formed with the elimination ofhydrogen sulphide.

2. A rubber product that has been vulcanized in the presence of thiobeta-beta-dinaphthylamine. I

3. A method of preserving rubber which comprises subjecting it tovulcanization in the presence of a material having the formula H I i N aR,

\S/ I I in which R and R are naphthylene groups.

4. A method of preservingrubber which comprises subjecting it tovulcanization in the presence of a reaction product of dinaphthylamineand sulphur.

5. A rubber product that has been vulcanized in the presence of areaction product of a dinaphthyl substituted amine, with sulphur.

6. A rubber product that has been vulcanized in the presence of thiodi-beta-beta-di naphthylamine. y

In witness whereof, I have hereunto signed my name.

Signed at and State of Ohio, U. S; A.,' this 7th day of Akron, in thecounty of Summit ALBEnTMpLIFFoRD.

